Charge controlled adaptive-optics system

Abstract

A charge controlled adaptive-optics system is disclosed for correcting phase distortion in a wavefront of a propagating optical wavefront in real time. In a preferred embodiment a selectively deformable piezoelectric mirror receives an incoming distorted optical wavefront and reflects it to a lenslet array optical sensor. The sensor generates a large plurality of focused light points, the offset positions of which represent wavefront tilts at a plurality of locations on the distorted wavefront. A misalignment calibration system calculates a plurality of calibration signals representing aberrations in the mirror surface and the sensor, and converts the signals into a plurality of representative light rays of varying intensity. The light ray are then superimposed on the light points to form a plurality of calibrated light points, which are then input to an electron-beam generating system. The generating system generates a plurality of electron beams of varying intensity that operate to supply and remove electrical charges from electrodes mounted within the piezoelectric mirror. The local electric fields induced by the charges result in a selective deformation of the piezoelectric mirror that corrects the distortion in the reflected wavefront.

We claim: 
     
       1. An adaptive-optics system for nulling phase distortion in a wavefront of a propagating wave, which is incident on an optical element, the system comprising: lenslet array-type sensor means for receiving the wavefront and generating a plurality of light points indicative of wavefront tilt at a plurality of locations on the wavefront;   image intensifier means for amplifying the light points;   compensation means for computing and superimposing compensation signals on the light points, thereby producing a plurality of calibrated light points;   electron beam generating means for converting the calibrated light points into a plurality of electron beams, the electron beams varying in intensity in relation to the calibrated light points and impinging a plurality of collectors within the generating means; and   wherein said optical element is a selectively deformable mirror including a monolithic piezoelectric wafer, a mirror surface adhered to a first side of the piezoelectric wafer, and a plurality of selectively chargeable electrodes mounted in the piezoelectric wafer, whereby receipt of the electron beams of varying intensity upon the collectors results in selective charging or discharging of the electrodes, thereby selectively deforming the piezoelectric wafer and the mirror surface adhered thereto to null the phase distortion in the wavefront incident on the mirror surface.   
     
     
       2. The system of claim 1, which further comprises calibration means for generating a second output representing a correction of aberrations present in the sensor means and the modulating means, the second output subsequently being superimposed on the first output, thereby creating a third output for input to the electron beam generating means. 
     
     
       3. The system of claim 2, wherein the calibration means comprises: interferometer means for generating an interferogram indicative of the aberrations present in the sensor means and the modulating means;   camera means for imaging the interferogram;   processing means for receiving an image of the interferogram imaged by the camera means and computing compensation signals for correcting the aberrations indicated by the interferogram; and   cathode ray tube means for receiving the compensation signals from the processing means and generating the second output, the second output being light rays of varying intensities emanating from the cathode ray tube means and representing the compensation signals supplied by the processing means.   
     
     
       4. The system of claim 1, wherein the electron beam generating means comprises: a vacuum contained charging system for selectively generating charging electron beams, the electron beams generated within the charging system being operable to supply the charges to the modulating means;   a vacuum contained discharging system for selectively generating discharging electron beams, the electron beams generated within the discharging system being operable to remove the charges from the modulating means;   a plurality of charging collectors housed within the charging system for receiving the charging beams, the charging collectors being operable to facilitate an accumulation of the charges thereon; and   a plurality of discharging collectors housed within the discharging system for receiving the discharging beams, the discharging collectors being operable to selectively remove the electrical charges from the modulating means.   
     
     
       5. The system of claim 4, wherein the charging and discharging systems each further comprise: at least one photocathode for receiving thereon the first output and emitting a plurality of electrons in response thereto;   at least one microchannel plate preamplifier means for amplifying the electrons;   at least one multi-channel plate amplifier means for further amplifying and focusing the electrons into a plurality of electron beams.   
     
     
       6. The system of claim 5, which further comprises a shielding element circumscribing the collectors, the shielding element having a voltage applied thereto to facilitate a vacuum-like receipt of stray electrons. 
     
     
       7. The system of claim 4, wherein the discharging collectors have an angled surface for facilitating displacement of electrons collected thereon when the collectors are irradiated by the electron beams. 
     
     
       8. The system of claim 1, wherein the electron beam generating means comprises: a vacuum contained electron beam charging system, the charging system being operable to supply electrical charges to the electrodes in the deformable mirror;   a vacuum contained electron beam discharging system, the discharging system being operable to remove the electrical charges from the electrodes.   
     
     
       9. The system of claim 8, wherein the charging and discharging systems each further comprise: at least one photocathode for receiving the light points and emitting a corresponding plurality of electrons from a reverse side thereof;   at least one microchannel plate preamplifier for receiving and amplifying the electrons;   at least one multi-channel plate power amplifier having a plurality of closely aligned channel holes, whereby electrons passing through the channel holes are further amplified and focused into the electron beams.   
     
     
       10. The system of claim 1, wherein the collectors are charging or discharging collectors, the charging collectors being operable to supply electrical charges to the electrodes, and the discharging collectors being operable to facilitate the removal of electrical charges from the electrodes, whereby selective charging and discharging of the collectors operates to selectively charge and discharge the electrodes, thereby selectively deforming the piezoelectric wafer.